Variable displacement pump



Nov. 20, 1962 Filed March 29, 1957 F. B. BURT 3,064,583

VARIABLE DISPLACEMENT PUMP 3 ShiZ-Sheet l .32 //6 Q //2 E j //0 26 j //422 g 404 4 4 ms //20 j m? INVENTOR.

FA gLow a. BURT.

A TTOR/V Y Nov. 20, 1962 F. B. BURT VARIABLE DISPLACEMENT PUMP 3Sheets-Sheet 5 Filed March 29, 1957 BY ATTOZNEY.

United rates 3,064,583 VARIABLE DISPLACEMENT PUMP Farlow B. Burt, SouthBend, Ind., assignor to The Bendix Corporation, a corporation ofDelaware Filed Mar. 29, 1957, Ser. No. 649,370 7 Claims. (Cl. 103-161)The present invention relates to positive displacement pumps having amovable stroke determining member whose position can be changed to varythe pump displacement, and more particularly to means for supporting andpositioning said movable member.

Positive displacement pumps of the type whose displacement can be variedusually employ a rotor having at least one fluid pressure chambertherein, and cooperating camming member which produces a reciprocatingmovement of the fluid displacement member in each fluid pressure chamberduring the rotation of the rotor. The displacement of the pump isdetermined by the relative positioning of the rotor and camming surface;and is usually varied by the positioning of the camming member inaccordance with either the discharge pressure of the pump, or thedifierential pressure across a flow control orifice. In most pumps ofthe above type, the reaction forces exerted against the camming membervary in direction and amount depending upon the angular position of therotor during its rotation to produce a fluctuating movement of thecamming member. This fluctuating movement of the camming member in turnproduces a corresponding variation in the pump displacement, andtroublesome noise and vibration in the pump and the system to which itis connected results.

It is an object of the present invention to provide a new and improvedpositive displacement pump whose output is varied in accordance withdischarge conditions, and which is so constructed and arranged thatchanging reaction forces exerted upon its displacement controllingmember will not be reflected in its positioning of the displacementcontrolling member.

A further object of the invention is the provision of a new and improvedpump of the above described type having control means which is easilyadjusted by control forces but which will not be moved by the reactionforces exerted upon it by the camming member.

A still further object of the invention is the provision of a new andimproved pump of the above described type whose camming member ismovable in a direction which changes the pump displacement, said cammingmember being controlled by a slide which is reciprocable generally atright angles to the camming members displacement changing motion, andbeing connected to the slide by means acting on a line of force whichnever overcomes the co-eflicient of friction between the slide and itssup porting member to effect a shifting of the slide. The camming memberand rotor preferably being so constructed and arranged that the forcesexerted upon the camming member decrease substantially to zero at someperiod during each revolution of the rotor, and at which timesubstantially no side loading is exerted on said slide so that the slidecan be accurately positioned with very little force exerted upon it byits control member.

A more particular object of the invention is the provision of a new andimproved radial piston pump comprising a rotor surrounding a pintlesuitably ported to provide suction and discharge for its cylinders atopposite sides of the pintle, a camming member surrounding the rotor andpivoted generally on the centerline of the are through which thecylinders discharge, and whereby arcuate movement about the pivotalsupport changes the displacement of the pumpsaid displacement changingmotion being restrained by a slide extending at generally right anglesto the camming members arcuate movement,

Patented Nov. 20, 1962 and which slide is connected to the cammingmember by means acting on a line of force which never overcomes thecoeflicient of friction between the slide and its supporting member.

The invention resides in certain constructions and combination andarrangements of parts, and further objects and advantages will becomeapparent to those skilled in the art to which the invention relates fromthe following description of several preferred embodiments describedwith reference to the accompanying drawings forming a part of thisspecification, and in which:

FIGURE 1 is a cross-sectional view of a radial piston pump embodyingprinciples of the present invention;

FIGURE 2 is a cross-section taken on the line 22 of FIGURE 1;

FIGURE 3 is a cross-sectional view taken on the line 3-3 of FIGURE 1;

FIGURE 4 is a cross-sectional view (having a portion broken away tobetter show details beneath the plane of the section) of an axial pistonpump embodying principles of the present invention; and

FIGURE 5 is an end view of a porting plate used in the pump shown inFIGURE 4.

The radial piston pump shown in FIGURE 1 generally comprises a bodymember A having an internal chamber 10 therein in which an annular rotorB is journalled about an axially extending pintle C which projects intothe internal chamber 10 from one end wall 12 of the pump. The oppositeend wall 14 of the pump is made in the form of a removable cover membersuitably bolted in place; and the annular rotor B is adapted to berotated about the pintle by means of a drive shaft 16 journalled in thecover member 14. The inner end of the drive shaft 16 is splined to adrive plate 18 positioned over the adjacent end of the pintle and theouter edges of which are fastened to the annular rotor B by means of aplurality of machine screws 20, only one of which is shown.

The annular rotor member B is provided with a plurality of radiallyextending openings 22, therethrough, the radially outer ends of whichare accurately counterbored to form cylinders '24 in which individualball pistons 26 are positioned. The ball pistons 26 are retained withinthe cylinder by means of an annular camming member D which extendsaround the outer surfaces of the rotor and on which the balls 26 areadapted to roll. The annular camming member D shown in the drawingutilizes the race 28 of a commercially obtained anti-friction bearing,pressed into a support member 30 which is suitablyguided and supportedfor eccentric movement with respect to the rotor B.

The pump shown in the drawing is adapted to be supplied with oil from areservoir 32 which is bolted directly to the top surface of the pump.Oil from the reservoir passes through a vertical opening 34 in the bodymember A to a longitudinally extending drilling 36 in the axiallyextending pintle C. The top surface of the pintle C directly beneath theannular rotor B is notched out as at 38 to provide inlet communicationbetween the inner end of the cylinders 24 and the inner end of thelongitudinally extending drilling 36; and a venturi section 40 ispressed into the longitudinal drilling 36 between the inlet passage 34and the notch 38 supplying the rotor. The particular embodiment shown inthe drawing utilizes a pressurized suction wherein fluid from the inletpassage 34 is forced into the throat of the venturi section 40 to thecylinders 24 by means of a high pressure impinging stream presently tobe described.

The radial piston pump shown in the drawings is adapted to be drivenclockwise as seen in FIGURE 2. The annular camming member D is supportedfor eccentric movement with respect to the annular rotor B by means ofan abutment pin 42 recessed into the lower end of -both the body memberA and the support member 30 in suchmanneras to limit all but a rockingmotion of the cam member D with respect to the rotor B. Maximumdisplacement for the pump will be provided when the cammingt member D isin the position shown in FIGUREZ of the drawing.- 'With the cammingmember Dsinthe-position shown; the ball pistons 26 willbe in theirinnermost position with respect to their cooperating cylinders 24whenthe inner end of the cylinders-24 are moved out of 'engagernent with theland portion 44 of the pintle-into communication with the inlet groove38 on the -upper= surface of: the pintle.

the -ball pistons 26 radially outwardly-in their'cooperat ing cylinders24 as theballs roll aroundthe race 28 to a position approximately 180from the start of the inlet stroke. As the 'ball'pistons approach theiroutward limit of-travel, the inner-end'of the cylinders 24 move out ofcommunication with the inlet groove 38 to-a position wherein a'lan-d 46valves otf orcompletely isolates the cylinders 24 from both suction anddischarge.

Continuedrotationof the rotor during the second half of each revolutioncauses the-ball pistons 26 to roll' around-the lower half 'of therace'28 thereby causingthe pistons 26 to be moved inwardlyto their mostinwardly 'or-starting'position. Just after the time that the ballpistons 26 start to move inwardly, the inner ends of thecylindersZdmoveoil the land 46 into communicationiwith a discharge groove- 48 in'thelower surface of th e' pintle C. The dischargegroove 48 isquitesimilar-to the inletgroove -38extending over a similar arc o'fthepintle, but is separated from the inletgroove' 38- Ey the land portions44 ;and146t- Fluid forced into thedischarge groove -48--'bythe inwardmovement of the'ball pistons 26 passes through a longitudinal dischargedrilling-50 in the pintle C to a transverse drilling 52 leading to adischarge -chamber 54 in the body member A. Some discharge fluid is-used forthe pressurizing of thepumps inlet stream by means ofa-transverse drilling 56 communicating the longitudinal dischargedrilling 50 with a nozzle 58 in the inlet drilling-36. The passage 56opens into an annular groove 60 in the nozzle 58; and atransversedrilling 62,, between opposite sides of the recess 60,communicates with-asmall longitudinal drilling 64 which directs-the highpressure-stream into the throat of the venturi section 40. Fluiddischarged from the pump passes-through an annular'filter 66 held intoengagementwith the bottom end" of the discharge chamber 54surroundingits inlet 68'-by m eans of a retainer 70 and a coil'spring-72. The coil-spring 72 is in turn held in place by'a threaded outletfitting 74- screwed into the outer-end of thedischarge-chamber 54. Thefitting '74 is 'provided with a centrally located discharge opening 76therethrough containing a checkvalve 78 and cooperatingvalve seat 80 forthe prevention of return flow through the pump; A bent wire 81 isinserted between the'ball 78 and atube fitting in the opening 76 toprevent the -b all'from restricting flow-out of the dischargeconnection.

The. pump shown in tl1e-drawing is adapted to' provide dischargepressures up to approximately 2500 pounds per square inch-at whichpressures 'sufiicient compressibility is encounteredinthe-oil circulatedthrough the pump to ,create a troublesome noise and vibration problem.In

The positioning of the camming 'member- D is suchthat" centrifugal forcemoves means of a transverse drilling 86 opening into the reservoir 82,and the outer end of which drilling is closed off by means of a ball 88pressed into a counterbore 90 in the outer end of the drilling: A smalltransverse drilling 92 of predetermined'size communicates thelongitudinal drilling 84 and the discharge groove 48 of the pintle tolimit the rate at which pressure flow is supplied the accumulator from'the discharge of thetpump.

Fluid pressure from the accumulator 82 .is used to pressurize each ofthe cylinders'24 when the ball pistons 26 therein have reached theiroutermost positions, and during the time that each cylinder is valvedoff from both the inlet groove 38 and-discharge groove 48by theland 46.Fluidtpressure from the accumulator 82 is-bled to each cylinder at'thisinstant in a controlled amount by" means of a small transverse drilling94 which communicates the accumulator passage 84 with the surface of thepintle C adjacent one side of the land 46. A plu--- rality ofcooperating drillings 96 (one for each of the cylinders 24) areprovidedin the annular rotor'Band are positioned in such away as toregister with the opening 94 during the time that each cylinder 24 isvalved off from both the suction and discharge grooves 38 and 48; Duringthetimes that the drillings'94 and 96 are in register,- fluid pressurefromthe accumulator 82'is communicated' to the cylinders 24; The grooves94 and 96 are further positioned such that the groove 96 moves out ofregister with the opening 94 just prior to the time that the cylinders24move-into communication withthe discharge groove 48. By means of'thisvalving process; each of the cylinders 24 are rapidly pressurized'to apressure approximately equal to the pump discharge pres sure priorto-the time that the individual cylinders are communicated to the pumpdischargesystem and imme' diatelyfollowing which the cylinders areopened .to pump discharge before leakage has had achance'to appreciablyreduce their pressure. It will be seen that this filling" of thecylinders with pressurefiuid prior'to valving to discharge isaccomplished from a pressure systemsubstantially isolated fromthe pumpdischarge system'the only connection-being thesmall transverse'drillingor filling orifice 92v which for all practical purposes preventsfluctu-' ations in accumulator pressure'from being transmitted to thepumps discharge system.

The displacement of the pump shown in the drawing is adaptedto becontrolled in accordance with the demand' of the system to which it isconnected. The pump will maintaina more or less constant dischargepressure ,withiii-certain limits; and as the demand'of the system formore fluid increases (as sensed by a slight drop in discharge pressure),the camming member'D is rotated to increase the pump displacement untilthe pump' again achieves its predetermined set discharge pressure.Conversely as thesysterns demand for pressure fluid falls oif, a slightincrease in pressure is sensed by the pump] causing its camming member'D to be shifted in a direc tion decreasing the displacement of the pumpuntilithe amount delivered equals the ,systems' demand at'thepredetermined set pressure of the pump.

The reaction forces exerted upon the camming member B bythe pistons 26varies in accordance with the number and the positioning of thepistons,.and the manner in which the cylinders are valved to the inletand discharge pressures. These reaction forces tendtoproduceafluctuatingmovement of the camming member, which 1f not'firmly resisted,would produce a rapid 'fiuctuation inthe displacement of the pump toproduce troublesome noise and vibration in the pump and the system towhich it is connected. According. to the principlesof the presentinvention, supporting and regulating means are provided for the cammingmember. which prevents the previously referred to fluctuating forcesfrom being transmitted back against the pumps controlsystem me manneraifecting the positioningof the camming member by the pumps controlsystem. The embodiment about to be described is constructed such thatthe fluctuating forces upon the camming member D will at some timeduring each revolution of the rotor substantially balance out, such thatno force is then exerted upon the pumps regulating or control system.Control movement may take place during these intervals of rotor movementto produce a precise positioning of the camming member D.

Although the annular camming member D may be otherwise supportedrelative to the body member A of the pump, the preferred embodiment willutilize an abutment positioned approximately on the center line of thedischarge cycle of the pump such that the line of force of the dischargepressure upon the rotor passes through the abutment. Displacementchanging movement of the camming member D takes place in a directionsubstantially at right angles to this line of force and is accomplishedin the preferred embodiment by arcuate movement of the camming memberabout the abutment 42.

According to the principles of the present invention, the displacementchanging movement of the camming member D is opposed by a slidereciprocable in a direction substantially at right angles with thedisplacement changing movement of the camming member. A suitableconnection is provided between the camming member and the slide tocontrol the movement of the camming member. In the preferred embodiment,the connecting mechanism between the camming member and slide will actupon a line of force extending at an angle relative to the slidingmotion of the slide which is greater than the coefficient of frictionbetween the slide and its supporting member under well lubricatedconditions. The fluctuating forces produced upon the camming memberduring the rotor pumping action under such an arrangement only serves toforce the slide into firmer engagement with the supporting member, andwill not move the slide to change the fluid displacement of the pump.

In the preferred embodiment the slide E is formed from a. cylindricallyshaped member positioned in a vertical drilling 102 in the body memberA. A U-shaped bracket 104 is welded to the adjacent end of the cammingmember D in such a position as to straddle the opposite sides of theslide E. A pin 106 is positioned across the outer ends of the U-shapedbracket; and the pin 106 is received in a milled slot 108 extending at aslight angle relative to the displacement changing movement of thecamming member. Reciprocation of the slide E therefore produces movementof the pin 106 at substantially right angles to the movement of theslide E causing the camming member D to pivot about the abutment pin 42.Camming member D is normally biased into its largest pump displacementproducing position by means of a coil spring 110 posi tioned between thebottom of the reservoir 32 and the lower end of the vertical drilling inthe slide E. The volume enclosed behind slide E is relieved to theinternal chamber of the pump by means of a drilling 114 communicatingthe vertical drilling 112 and the upper end of the slot 108, and thechamber 110 is in turn communicated with the reservoir 32 by means ofthe drilling 116 in the upper end of the body member A. An adequatesupply of lubricating fluid is therefore assured all moving parts of thepump; and any high pressure leakage is ade quately relieved to thesystems reservoir.

Shifting movement of the slide E in the embodiment shown in the drawingis accomplished by the utilization of a slight change in pressure of thedischarge pressure of the pump. Inasmuch as the fluctuating forcesproduced upon the camming member during operation of the pump are in theorder of from 50 to 100 pounds; the design of the pump is such thatthese forces pass through a null during each revolution of the rotor andthe construction of the slide and cam shifting structure is such thatthe fluctuating forces do not tend to shift the slide, very little forceis required for moving the slide. A hydraulic piston 118 is positionedin a bore 120 in the body member A directly 6 beneath the lower end ofthe slide member E. Fluid pressure supplied to the lower end of thehydraulic piston 118 forces it up into engagement with the lower end ofthe slide E to oppose the coil spring and efiect a shifting of the slideE. Inasmuch as the forces required to shift the slide are quite small, acontrol valve F is utilized to regulate the amount of the pump dischargepressure which is supplied to the hydraulic piston 118. The structureshown comprises a bore 122 having a spool valve 124 therein, the annularflanges or lands of which normally straddle a control port 126 which iscommunicated to the bottom side of the hydraulic piston 118 by suitabledrilled passageways. The inner end of the bore 122 of the control valveis communicated with the discharge drilling 50 in the pump pintle C by adrilling 128, and the outer end of the bore 122 of the control valve iscommunicated with the pump chamber 10 by means of an opening 130 in thebody member A. The outer end of the spool valve 124 projects into aspring chamber 132 where it is abutted by a spring retaining plate 134which is biased inwardly by a coil spring 136. The outer end of thespring chamber 132 is closed off by a suitable sealing member 138 heldin place by the threaded outlet fitting 74; and the spring chamber 132is also vented to the internal chamber 10 by means of a drilling 140 inthe body member.

Operation of the pump should be readily discernible by those skilled inthe art from the above description reciting the cooperation between thevarious pump elements. Suffice it to say that hydraulic fluid from thereservoir 32 passes through the inlet passageway 34 to the venturisection 48 where the impingement of a high pressure stream through thelongitudinal drilling 64 into the throat of the venturi section producesa positive pressure in the inlet groove '38 of the pintle C. Rotation ofthe rotor B successively communicates the cylinders 24 with the inletgroove 38 during the portion of the rotor cycle wherein the ball pistons26, which are in rolling contact with the camming member D, moveradially outwardly in their cylinders. Outward movement of the ballpistons 26 causes a quantity of fluid to be added to each cylinder whilethe cylinders are communicated to the inlet groove 38; and atapproximately the time that the ball pistons 26 have reached their outerlimit of travel, the inner openings of the cylinders 24 slide over theland portion 46 of the pintle to isolate the cylinders fromcommunication with both the inlet and outlet systems of the pump.Shortly after the cylinders 24 become valved off from the inlet groove38, and prior to the time that the cylinders are communicated withdischarge groove 48 of the pintle, each cylinder is pressurized withfluid from the accumulator 82 by the rotation of each cylinderspressurizing groove 96 into communication with the pressurizing groove94 of the pintle. Each cylinder is thereby rapidly brought up to apressure approximating that of the pump discharge pressure; andimmediately thereafter each chamber is successively valved off from theaccumulator, and then communicated with the discharge groove 48 of thepintle. Continued rotation of the rotor with respect to the cammingmember D causes the ball pistons 26 to move inwardly in their cylinders24 discharging the fluid into the discharge groove 48, throughpassageways 50 and 52 in the pintle to the discharge chamber 54. At thesame time a small side stream is supplied to the suction pressurizingnozzle 58 through the transverse drilling '56; and a second side orauxiliary stream of high pressure fluid is supplied to the accumulator82 through the small filling orifice 92 extending between the dischargegroove 48 and the accumulator passage 84 of the pintle. It should bestated that the accumulator 82 is sized sufficiently large to controlits pressure drop within limits each time a drilling 96 is communicatedwith the drilling 94; and the passageway 92 is sized suflficiently largeto maintain the reservoir 82 at a pressure approximately equal to thatof the pump discharge, while at the same time preventing thecpressuresurges experienced within the accumulator 82-:from reaching; thedischarge system of the pump.

It has: previously been explained. that the positioning of the abutmentpin 42 issucli that the line of force of the. pressure forces upon therotor. pass substantially through the center of the pin 42. Continuouslychanging forces produced upon the camming member as the individualcylinders are valved'to suction and-discharge, produce fluctuating.componentstending to alternately rock the: camming member to oppositesides of the abutment pin 42. Fluctuating movement of the camming memberD is restrained by the slide structure E which is rigidlysupported-against movement in this direction, but which is positionableat substantially right angles to. the fluctuating forces. appliedto thecamming member. The slot 108 which receives the pin 106'attached to thecamming member D. isprefera'bly formed at a shallow enough angle withrespect to. thedirection of'fluctuating movement of the cammingmembersuchthat the component of these forces in thedirection-of' movement ofthe slide will not overcomethe. coeflicient of.'friction between theslide and its-receivinggroove 102. The flilctuating forces on thecamming member Dtherefore produce a locking action of the. slide E inits receiving groov which prevents these forces from being .transmittedbackrinto the control system adapted to position the slide E.

The .slide Elis positioned by means of the fluid pressure piston118whichreceives itsactuating pressure from the discharge. of. the'pump througha control valve F; As pressure is .admitted'to. the inner end of thespool valve 124,,it's forceonthe spool'valve is exerted'against the coilspring136j Uponsyielding of'the-coil spring 136 (which Will-occur at apredetermined set pressure). the spool valves inner land 142'willbemoved sufiiciently to. communicate the pump discharge pressure in theinner endof'the bore 122to thecontrol passage leading to the lowerendof'the hydraulic piston 118'. Should the adjustment ofthe cammingmemberD be such as to provide a-.greater. amount of pressure. fluidthanis being used by the system to which-the. pump is: connected, .theback pressure exerted *by the. system will be. reflected in anincreasedidischarge. pressure of. the. pump-resulting intheopeningof-thecontrol passage to the pump discharge pressure aspreviously explained.This pressure against the. lower. end of the hydraulic piston 118-forcesit upwardly toengagement with.the lower end of the. slide E to exert anadditional amount of force upon the slide in op.-

po'sition to the.coil springllt); As previously indicatedthe fluctuatingforces on the camming member D alternatelyforce the pin 106 in oppositedirections-during each revolution of the rotor to produce nulls duringwhich no rocking forces are-being exert-ed upon theslide. The increasedforce exerted upon the hydraulic piston 118 as a resultin the rise inpressure in the pump discharge is therefore free to move.the slideEduringth'ese null conditions without being opposed by the fluctuatingforces produced.upon.the cammingimember during the pump operation:Upwardmovement of. the slide E'produces a rockingaction of the cammingmember D about the abutmentpin'4z in'adirection decreasing the pumpdisplacement, and will continue to'do'so until the'amount of fluid beingdelivered by the pump just balances the consumption of the system towhich it is connected at a pressure corresponding to the predeterminedset pressure of thepump as controlled by the biasing action of the coil8 vided in the end plate 152 for the reception of a drive shaft 156. Theouter end of the drive shaft 156 is journalled by anti-friction means ina bearing plate 158, suitablybolted to the end plate 152, and the innerend of the drive shaft 156 is journalled in a sleeve 160 pressed' intothe inner end of-the axially extending opening 154 and projecting intothe pump internal chamber 150. A rotor member H comprising a generallycylindrical shaped body section 162 having an end closure plate 162"brazed thereto is journalled about the inner end of the sleeve 160. Thesleeve 160 is received into an axially extending opening 164 in the bodyand'closure members and a splined bushing 166 is pressed into theopening to.

provide a driving connection with the inner end of the shaft 156.

The rotor member H is provided with a plurality of axially extendingcylinders-168 uniformly spaced about its axis of rotation, and only oneof which is shown in the drawingseach having a cooperating. piston 170'therein. The inner end of each piston 170 is bored out, as at 174, toreceive a coil spring 176 which is positioned between the end closureplate 162 and the bottom of the bore to bias the pistons outwardly withrespect to their cylinders 168. The outer end'of each piston 170 isspherically shaped to receive the ball end 178 of a slipper shoe 180,the other end of which bears against a bearing plate 182 suitablyretained on the inner face of a tiltable swash plate 184. The slippershoes 180 will normally be biased. against the bearing plate 182 bypressure forces during'the pumping operation of the unit; and areadditionally 'heldadjacent the bearing plate 182 by anannular'spider'plate186 which is suitably, recessed around its peripheryto extend over'a portion of each shoes fiange138. The spider plate 186is retained' adjacent the bearing plate 182 by means of a spacer member190. A suitable counterbored opening 192 is providediin the spacermember to receive the headed end of a.-bolt'194, the other endofwhichextends through a bushing'196 is locked'inplace by a-nut'198.The'bushing 196 is positioned in an opening 200 extending through theswash plate'184 behind the bearing plate 182, and is held in position bythe inside face o'f'the hear ing plate 182.

The rotation of therotor member H aboutthesleeve 160 causes the slippershoes to slide aroundthe'periphery' of the bearing plate 182 to producea reciprocation of the pistons 170 in'their'cylinders'168. The pumpshown in the drawing is adapted to be rotated in a clo'ckwisedirectionas viewedfrom the shaft'end of thepump; and as such the pistons 170 willmove outwardly-with respect to their cylinders 168, as the-piston movesfrom the position shown in the drawings to a position adjacent the upperend of'F-IGURE 4; During this outward movement of the pistons 170, fluidis introduced into the cylinders 168 through an inlet opening 202 in therotorclosure plate'162 and an arcuately shaped inlet po'rt204 in aporting plate 206 positionedbetween the outer end" ofthe rotor member Hand the removable end-plate 152 of the pump. The arcuately'shaped inletport'204 com-- municates with-suitable drilled passageways'inthe bodyportionof the pump--which inlet passageways are not showninthedrawingsin'asmuchas they are positioned in the portion of thepump'lying' above the plane of'the paper.

Clockwise rotationof the cylinders 168, during the second half of eachrotor revolution, carries the pistons 170 from a" position adjacent theupper end of the swashplate 184 to the lower position shown inthe'drawings; The pistons170 during this halfof the cycle are biasedinwardly by'the' sliding action of' the shoes 180' on the bearing plate182. Inward movement of the pistons'170 forces fluid out of thecylinders 168 through the openings 202 in the rotor closure plate 162'to an arcuately shaped dischargeport 208 in the other half. of theportingplate 206. Pressurefluid from the pressure port 208 passesthrough a discharge passageway 210 in the front cover plate 152 to adischarge connection 212.

The swash plate 184 is preferably pivoted about a point positioned onthe center line of the pump such that the forces exerted upon the swashplate will produce a fluctuating movement tending to alternately rotatethe swash plate in opposite directions to produce null periods whensubstantially no tilting force is exerted thereon. The structure E usedin this embodiment for controlling the swash plate is similar to thatdescribed for controlling the camming member of the previous embodiment.The swash plate 184 is journalled about opposite pin sections fixed inthe side walls of the body member, and is provided with a bifurcatedportion 216 carrying a pin 218 which is received in a groove 22G milledinto the slide 222. The slide 222 is generally cylindrically shaped andis received in a bore 224 extending at right angles to the axis of thepump, and the upper end of which bore is closed off by means of athreaded closure member 226. The upper end of the slide 222 is bored outin similar fashion to that of the previous embodiment, and a coil spring230 is positioned between the closure memher 226 and the bottom of thebore 228 to bias the slide downwardly towards the center line of thepump. The groove 22!) is inclined angularly with respect to the centerline of the pump such that reciprocatory movement of the slide 222 willtilt or rock the swash plate 184 about its pin sections 214 from aninclined position producing a maximum stroke of the pistons 170 to agenerally parallel relationship with respect to the rotor 162 whereinsubstantially no stroke of the pistons 170 is produced.

The positioning of the slide 222 in this embodiment is accomplished bystructure similar to that of the previous embodiment. Inasmuch as verylittle force is required to move the slide 222, and this pump also isadapted to produce extremely high discharge pressures, a control valve Fsimilar to that of the previous embodiment is provided to regulate theamount of pressure delivered to the slide opposing piston 232. The slideopposing piston 232 is positioned in a bore 234 beneath the slide 222 inthe body member G, and is supplied with pressure from the control port236 of the control valve F. The control port 236 communicates with anextension 238 of the discharge passage 210 in which a spool valve 240similar to that of the previous embodiment is positioned. The pumpdischarge pressure is therefore applied to the inner end of the spoolvalve 240; and the outer end of the spool valve 240 projects into aspring chamber 242 where it is abutted by a spring abutment plate 244biased inwardly by the coil spring 246. The other end of the coil spring246' is held in place by a threaded closure member 248 which is screwedinto the outer end of the spring chamber 24-2. An exhaust passage 250communicating with the pump internal chamber 150 is provided for thatportion of the valve bore 238 which is positioned on the opposite sideof the control port 236 from the portion containing the pump dischargepressure.

The control valve F and the slide structure E operate in a similarfashion to the corresponding portions of the preceding embodiment andwill not be described in detail. Suffice it to say that an increase inpump discharge pressure above the predetermined set pressure asdetermined by the spring 246, causes a shifting of the spool valve 240to admit additional pressure to the bottom side of the piston 232 toproduce an upward shifting of the slide 222 during those portions oftherotor cycle wherein substantially no rocking forces are exerted upon theswash plate 184. Upward movement of the slide 222 will of course causethe swash plate 184 to gradually assume a position more nearly parallelwith respect to the rotor 162, until the displacement of the pumpsubstantially corresponds to the consumption of the system at thepredetermined set pressure of the pump. A decrease in pump dischargepressure permits the spring 246 to bias the slide valve 240 inwardlyuntil the con- 1G trol port 236 is communicated with the passage 250,whereupon the pressure in control port 236 is decreased sufficiently topermit the slide 222 to be moved downwardly into a position increasingthe pump displacement sufiiciently to balance the consumption of thesystem to which the pump is connected.

Although the invention has been described in considerable detail, I donot wish to be limited to the particular constructions shown anddescribed; and it is my intention to cover hereby all adaptations,modifications and arrangements thereof which come within the practice ofthose skilled in the art to which the invention relates.

I claim:

1. In a positive displacement hydromechanical device: a body member,first and second members in said body member at least one of which firstand second members rotates relative to the other, at least one positivedisplacement means operatively connected between said first and secondmembers so as to produce chambers Whose volume varies during relativerotation between said first and second members, one of said first andsecond members also being movable in a first direction relative to theother of said members in a manner changing the displacement of saidchambers, a slide in said body member held against movement in saidfirst direction, said slide being reciprocable in a direction generallyperpendicular to said first direction, and a mechanical connectionbetween said slide and said one of said first and second members whichtransfers tension and compression forces therebetween in a directionwhich diifers from a normal to the direction of movement of said slideby an angle whose tangent is less than the coefiicient of frictionbetween said slide and said body member, whereby said one of saidmembers is held by 'said slide against fluctuating movement producedduring operation of the device, and whereby the displacement of saiddevice can be varied by the positioning of said slide.

2. In a radial piston hydromechanical device: a body member having aninternal chamber therein having a longitudinal axis with first andsecond generally mutually perpendicularly extending imaginary planespassing through said axis, an axially positioned rotor having at leastone generally radially extending fluid pressure chamber therein, a cammember positioned about said rotor member, a piston in said fluidpressure chamber extending radially outwardly thereof for engagementwith said cam member, inlet and outlet porting on opposite sides of saidfirst imaginary plane for successive communication with said fluidpressure chamber during rotation of said rotor, pivot means positionedon one side of said first imaginary plane and pivoting said cam to saidbody member to permit arcuate movement of said cam about said pivotmeans in the general direction of said first plane, a slide in said bodymember generally paralleling said second imaginary plane and restrainingmovement of said slide in the direction paralleling said first plane,and slot and pin means connecting said slide and said cam member, thesides of said slot being generally in abutment with opposite peripheraledges of said pin and extending at an angle relative to said secondimaginary plane whose tangent is less than the coefiicient of frictionbetween said slide and body member, whereby said cam is held by saidslide against fluctuating movement produced during operation of thedevice, and whereby the displacement of said device can be varied by theshifting of said slide.

3. In a radial piston hydromechanical device: a body member having aninternal chamber therein having a longitudinal axis with first andsecond generally mutually perpendicularly extending imaginary planespassing through said axis, a pintle in said chamber centered on saidaxis, a rotor positioned about said pintle and having at least onegenerally radially extending fluid pressure chamber therein, a cammember positioned about said rotor member, a piston in said fluidpressure chamber 3,0e4,5sa

inary plane for successivecommunication with said flilid' pressurechamber during rotation of said rotor, abutment means positioned on oneside of said first imaginary plane connecting-said cam to said bodymember and permitting movementof said cam-in the direction.of said firstimaginary plane, a. slidein saidbody, memberheld against motion exceptin a directionngenerally paralleling said second imaginary plane and-psitioned-to one side thereof, said slide and body member having acoefficient of sliding friction therebetween opposing movement of saidslide, a. mechanical connection transferring tension and compressiveforces from said cam to said slidelat an. angle relative to a normal tosaid second imaginary planethe tangent of which angle does not exceedsaid coefiicie nt offrictiomand means for positioning said slide 4. In aradial piston pumpz' a body memberhaving an internal chamber thereinhaving a-longitudinal axis with first and second generallymutually-perpendicularly extending, imaginary planes passing throughsaid axis, a: pintle in said chamber centered on said axis, a rotorpositioned about said pintle and having at least one generally. radiallyextending fluid pressure chambers therein, a cam member-positioneda'boutsaid rotor member, apiston in said fliiidi pressurechamber extendingradially outwardly thereof for engagement with said cam member; saidpintle having-inlet and outlet porting on opposite sidesof said firstimaginary plane for successive"communicationwith said fluidpressurechamber during rotation. of; said rotor pivotal'abutment meanspositioned on thedischargestroke sideof saidfirstimaginary planeconnecting saidtcamuto. said body member and permitting, arcuatemovement of said cam in the direction of said vfirst imaginary plane, a.cylindrical bore in said body member generally perpen-- dicular to saidfirst imaginary plane and positioned to oneside of. said secondimaginary plane, aslide in said bore,:slot and pin means connecting saidslide andisaid: cam: member, the sides ofv said slot being generally inabuta ment with opposite peripheral edges of a said pin a and :ex;tending at an angle relative' to said secondlimaginary'-= plane thetangent of which angle is less thanthe coeflicient': of:friction betweensaid slide and body; member; whereby, said cam is 'held by said slideagainstfluctuating move' ment produced during operation of :thepump andwhereby the displacement of said pumpcan be varied bythe'shiftirigv of-said slide,- means biasing saidslide'to its position pro ducing,maximum stroke vof-said piston, and meanszusing: pressure-discharge ofsaid pump totbiaslsaid slidezin the opposite direction tovdecrease'the-stroke of said piston.

5. Inarotary axial piston pump: a body member h'avving achamber therein,,arotor'in said :chamber journalled for rotation about an" axisextending through said cham ber,1said rotor havinganendsurfaceaextending generally transversely to said axis, at least onegenerallyaxially: extending; chamber in said rotor with an opening: tosaid end surface, 1 a" swash plate i adjacent said end. surface ofi saidrotor andjourn'alled for pivotal movement with: re'-.- spect thereto,a'fluid displacement member in.'said' cham-'-' berand operativelyconnected tosaid swashiplate to be stroked thereby, aslide in said bodymember held against:

movement intan axial direction but slida-ble'in a direction generallytransverse towsaid axis, and meansconnecting: said:slide-an'd saidswashplate in a manner transferring compression and tension forcestherebetweenat an-anglei relative. to a normal to thereciprocatingmovement of said slide; the tangent. of-.which angleis'less than the:

12 coeflicient of friction between said slide and body membet.

6. Irra rotary, axial piston pump: a body member having ,a chambertherein, a rotor in said chamber journalled for rotation about an axisextending through said chantber, said rotor having an end surfaceextending generally? transverselyto said'axis, at least one generallyaxially extending cylinder chamber in said rotor with an' opening tosaidv end surface, a swash plate adjacent saidfend surfaceof said rotorand journalled for pivotal movement. with respect thereto, a fluiddisplacement member in said. cylinder chamber and operatively connectedto said swash plate totbe stroked thereby, a slide insaid body member,held against-movement in an axial direction but slidable in a directiongenera'lly'transverse to. said-axis, and slot and pin meansconnectingsaid slide and said swash plate, the sides of said slot beinggenerally, in-abut-ment with. opposite peripheral edges of .said pin,andlextending at an angle relative to a normal to said axis, .thetangent of: which angle is less than the coefficient of friction betweensaid slide and body members, whereby said. swash plate is held by saidslide against fluctuating movement EPIC duced during operation ot thepump, and whereby the displacement of-said pumpis-varied by thepositioning ofl said slide.

' 7. In aerotary axial piston pump: abody memberhaye ing achamber-therein, a rotor 'in said chamber journalled: for rotation aboutan axis extendingthrough said cham her, said rotor having an end suriaceextending generally transverselywto said axis, at least one.generally'axially ex-' tending cylinder chamber in saidrotor withlanopening to said end surface, a swash plate adjacent said end S1117.face of a said rotor: and journalled for pivotal movement with. respectthereto about. an axis generally'passing through said-firstmentioned-axis,-.afluid displacement. member in said cylinder chamberand operativelyconnected -to.said'swash plate 'to' be stroked thereby,a--.slide;-

in said 'body; member held against movement in an axialdirection' butslidable in a direction generally transverse to said firstmentioned-axis, and slot and pin'means con-:- necting said slide andsaid swash plate; the sides of said slot beinggenerally in abutment withopposite-peripheral edges of said' pin and extending at: an angle'relative to a; perpendicular plane to said first mentioned; axis, said:angle havinga'tangent which is less thanthe coefficient: of frictionbetween'said slide and body member, means; biasing said slide in adirection whichrproduces maximum stroke ofsaid fluid"displacementmember,andlmeansusingflpressureidischarge vof said pump to bias said slide :in:the opposite direction reducing the strokeofsaid:iluid dis' placementmember:

ReferencesCited-inthe file of this patent I UNITED STATES 3 PATENTS

